Knobology Flashcards
Ultrasound waves lose some energy to the tissues they pass, a process called ____.
- The energy lost is converted into a negligible amount of heat
- The rest of the energy is reflected towards their source (____)
Ultrasound waves lose some energy to the tissues they pass, a process called attenuation.
- The energy lost is converted into a negligible amount of head
- The rest of the energy is reflected towards their source (echo)
Liquid (blood urine) appears –> __ (minimal resistance, and therefore no echo)
solid organ (liver/spleen) –> ___
bone –> reflects all sound waves, All of the reflected energy shows up at bright, ____ area at the surface. No image can really be seen through it.
Gas: ultrasound waves that encounter gas are deflected in all directions –> ____
○ Appears like a “grey snowstorm”
Liquid (blood urine) appears –> black (minimal resistance, and therefore no echo)
solid organ (liver/spleen) –> grey
bone –> reflects all sound waves, All of the reflected energy shows up at bright, white area at the surface. No image can really be seen through it.
Gas: ultrasound waves that encounter gas are deflected in all directions –> scatter
○ Appears like a “grey snowstorm”
- Frequency increases = penetration ____
- Frequency decreases = penetration ____
- Frequency increases = resolution ____
Frequency decreases = resolution ____.
- Frequency increases = penetration decreases (ex in linear probe)
- Frequency decreases = penetration increases (ex in curvilinear probe)
- Frequency increases = resolution increases
Frequency decreases = resolution decreases.
What is axial resolution
ability of the waves to distinguish between two objects at different depths.a
axial resolution improves as ___ increases. A probe of __- frequency is therefore better able to distinguish between two structures.
axial resolution improves as frequnecy improves.
The indicator is always oriented towards the patient’s ___, or towards the patient’s head
The indicator is always oriented towards the patient’s right, or towards the patient’s head
How does Gain work
Gain: more energy output, allows more energy to return to the probe proportionally.
- The image on the screen appears whiter/brighter.
- Allows you to electronically increase the sensitivity of the probe
- If you want to make an echogenic (white) structure stand out, you would increase the gain. If you were most interested in an anechoic (dark) area, you would decrease the gain.
Time gain compensation (TGC): allows you to fine tune the gain at a specific depth while leaving the rest of the field unaffected.
What is refraction
when US waves are deflected from their original path by passing close to a large, cruved smooth walled structure (like a bladder)
result is a shadow-like image that seems to project from the edges of the curved structure
Acoustic shadowing
when US waves hit something that blocks their path (usually bone), everything behind the blocking structure appears black.
- The black streak then cuts across the tissue planes and body cavities.
It is far too linear to be mistaken for free fluid, which is always irregularly shaped.
Acoustic enhancement
When US waves go through an area of LOW resistance (fluid), the tissues on the far side glow more brightly than the tissues beside them.
- The waves go through the fluid without any difficulty and therefore retain nearly all of their energy. Upon entering denser tissue on the far side, this excess energy makes the tissues beyond the fluid-filled structure light up more brightly than adjacent tissues
- Seen in gall bladder, or any fluid-filled cystic or vascular structure.
Reverberation
when a high density structure (needle) replicates itself
___ are echo signals and images that do not accurately represent the tissue.
Artifacts.
___ is an anechoic signal caused by failure of the sound beam to pass through an object
shadowing
___ occurs when an object attenuates less than other surrounding tissues, which is commonly seen as a hyperechoic or bright area on the farside of a fluid-filled structure
enhancement
___occurs when a sound wave is reflected back and forth between two highly reflective interfaces, and the time delay is interpreted by the machine as a coming from a greater distance.
reverberation
